[SPARK-9212] [CORE] upgrade Netty version to 4.0.29.Final

related JIRA: [SPARK-9212](https://issues.apache.org/jira/browse/SPARK-9212) and [SPARK-8101](https://issues.apache.org/jira/browse/SPARK-8101)

Author: Zhang, Liye <liye.zhang@intel.com>

Closes #7562 from liyezhang556520/SPARK-9212 and squashes the following commits:

1917729 [Zhang, Liye] SPARK-9212 upgrade Netty version to 4.0.29.Final

pom.xml

@@ -573,7 +573,7 @@
       <dependency>
         <groupId>io.netty</groupId>
         <artifactId>netty-all</artifactId>
-        <version>4.0.28.Final</version>
+        <version>4.0.29.Final</version>
       </dependency>
       <dependency>
         <groupId>org.apache.derby</groupId>